linux-kernel - Re: [PATCH 06/16] lib/test_bitmap: delete meaningless test for bitmap

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Message-ID: <YtXMjwXnRIT+YHg7@smile.fi.intel.com>
Date:   Tue, 19 Jul 2022 00:11:43 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Alexey Klimov <aklimov@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Ben Segall <bsegall@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dennis Zhou <dennis@...nel.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Eric Dumazet <edumazet@...gle.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Ingo Molnar <mingo@...hat.com>,
        Isabella Basso <isabbasso@...eup.net>,
        John Fastabend <john.fastabend@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        KP Singh <kpsingh@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Martin KaFai Lau <kafai@...com>,
        Mel Gorman <mgorman@...e.de>, Miroslav Benes <mbenes@...e.cz>,
        Nathan Chancellor <nathan@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Song Liu <songliubraving@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tejun Heo <tj@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Valentin Schneider <vschneid@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Vlastimil Babka <vbabka@...e.cz>, Yonghong Song <yhs@...com>,
        linux-mm@...ck.org, netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH 06/16] lib/test_bitmap: delete meaningless test for
 bitmap_cut

On Mon, Jul 18, 2022 at 12:28:34PM -0700, Yury Norov wrote:
> One of bitmap_cut() tests passed it with:
> 	nbits = BITS_PER_LONG;
> 	first = BITS_PER_LONG;
> 	cut = BITS_PER_LONG;
> 
> This test is useless because the range to cut is not inside the
> bitmap. This should normally raise an error, but bitmap_cut() is
> void and returns nothing.
> 
> To check if the test is passed, it just tests that the memory is
> not touched by bitmap_cut(), which is probably not correct, because
> if a function is passed with wrong parameters, it's too optimistic 
> to expect a correct, or even sane behavior.
> 
> Now that we have bitmap_check_params(), there's a tool to detect such
> things in real code, and we can drop the test.

There are no "useless" tests. Same comments as per a couple of previous
patches.

-- 
With Best Regards,
Andy Shevchenko